Morphological limits and comparisons with N. cremoriventer, which is similar in some external and cranial traits, were reported by Musser (1973c, 1981b); also reviewed by Corbet and Hill (1992). Dao and Cao (1990) described quangninhensis as a subspecies of Rattus cremoriventer (= N. cremoriventer). Niviventer cremoriventer occurs in Indochina only south of the Isthmus of Kra (see that account), but N. langbianis is still referred to as either Rattus cremoriventer or Niviventer cremoriventer in most of the current Vietnamese (Dang et al., 1994) and Chinese (Zhang et al., 1997) literature. One out of the several distinct traits characterizing N. langbianis is its monocolored brown tail, which is the feature used by most researchers to separate the species from specimens of N. fulvescens, but the tail ranges from bicolored to monocolored brown in N. fulvescens and those with brown tails are often misidentified as N. langbianis. Even examples of Indochinese Rattus, which generally have unpatterned monocolored brown tails, have been identified as N. langbianis (Musserís observations from study of museum collections). Throughout its range, N. langbianis is found with N. fulvescens in the same habitats. We have depended solely upon our study of specimens (except for the Cambodian sample) for the distribution outlined above. Kuznetsov (2000) recorded the species (as cremoriventer) from three islands off the coast of N Vietnam; Wang (2003) listed it from Yunnan Province in W China (as N. cremoriventer indosinicus); and Zhang et al. (1997) mapped records in the provinces of Sichuan, Guizhou, and Yunnan in S China; identity of these specimens, however, has to be verified, especially those from Sichuan and Guizhou, which seem too far north and may represent N. confucianus with monocolored brown tails. Niviventer langbianis has been collected in far N Vietnam west and east of the Red River (Lunde et al., 2003b; Musser, 1973c and specimens in AMNH, IEBR, and MVZ). NE India and N Vietnam are the northern extremes of N. langbianis documented by specimens; whether this arboreal species also occurs in S China where tropical evergreen rainforests have not been destroyed has yet to be determined. Karyotype of sample from Dalat Plateau in Vietnam recorded by Baskevich and Kuznetsov (2000).